Crystal structure of a (25R)-2 alpha,3 alpha-epoxy-5 alpha-spirostan-6, 23-dione hemi-ethyl acetate solvate

The compound (25R)-2 alpha ,3 alpha -epoxy-5 alpha -spirostan-6,23-dione, c rystallizes as a hemi-ethyl acetate solvate, having two host molecules of s imilar conformation per molecule of ethyl acetate, in the asymmetric unit. The O atom of the epoxy group is alpha -oriented. The presence of the epoxy group disturbs the chair conformation in the ring A of the steroidal nucle us. Ring A has a C5 alpha ,C10 beta half-chair conformation. The six-member ed rings B, C, and F have chair conformation as expected. The D ring adopts a C14 alpha -envelope conformation and the E ring is midway between a C22 alpha ,O3 beta half-chair and a C22 alpha -envelope conformations. The A/B, B/C, and C/D ring junctions are trans. Crystal data: C27H38O5.(1)/2C4H8O2, Monoclinic, space group P2(1), a = 7.7363(18) b = 28.769(12) c = 12.038(6) Angstrom, beta = 90.88(5), V = 2679.0(10) Angstrom (3), Z = 4. The packing of the molecules is assumed to be dictated by van der Waals interactions a nd by intermolecular C-H...O hydrogen bonds.